Add video decoding methods in Decryptor and add DecryptingVideoDecoder.

media/media.gyp

Index: media/media.gyp
diff --git a/media/media.gyp b/media/media.gyp
index 02d9ca5e203a8440cdbb7111f785dee2934ed9a0..c617d5eba23d1bc5a25ca8086fcdf1304f36bb69 100644
--- a/media/media.gyp
+++ b/media/media.gyp
@@ -249,6 +249,8 @@
         'filters/audio_renderer_impl.h',
         'filters/chunk_demuxer.cc',
         'filters/chunk_demuxer.h',
+        'filters/decrypting_video_decoder.cc',
+        'filters/decrypting_video_decoder.h',
         'filters/dummy_demuxer.cc',
         'filters/dummy_demuxer.h',
         'filters/ffmpeg_audio_decoder.cc',
@@ -628,6 +630,7 @@
         'filters/audio_renderer_algorithm_unittest.cc',
         'filters/audio_renderer_impl_unittest.cc',
         'filters/chunk_demuxer_unittest.cc',
+        'filters/decrypting_video_decoder_unittest.cc',
         'filters/ffmpeg_audio_decoder_unittest.cc',
         'filters/ffmpeg_decoder_unittest.h',
         'filters/ffmpeg_demuxer_unittest.cc',